1. Field of the Invention
The present invention relates to a liquid supply apparatus which supplies a liquid and a liquid discharge apparatus which discharges a liquid from a nozzle.
2. Description of the Related Art
In a certain ink-jet head for discharging a ink from a nozzle, the ink is supplied from a subtank (liquid supply apparatus) provided between an ink cartridge and an ink-jet head. For example, in an ink-jet recording apparatus described in Japanese Patent Application Laid-open No. 2006-247936, an ink-jet head and a subtank are arranged on a carriage, and the ink is supplied from the subtank to the ink-jet head. An atmospheric air communication hole is provided on the upper surface of the subtank. The atmospheric air communication hole is covered with a gas-permeating film. Accordingly, the gas contained in the subtank is discharged from the atmospheric air communication hole to the outside. Therefore, the liquid contained in the subtank can be separated from the gas. It is possible to avoid any invasion of the gas into the ink-jet head.
In the ink-jet head recording apparatus described in Japanese Patent Application Laid-open No. 2006-247936, the carriage makes the reciprocating movement in the predetermined directions. Therefore, the pressure fluctuation arises in the ink contained in the subtank. It is feared that the discharge characteristic of the ink may be varied or fluctuated in the ink-jet head due to the pressure fluctuation. On the contrary, the present inventors have contrived that a damper film is provided for a subtank in order to suppress the pressure fluctuation of the ink as described above. Further, the present inventors have made the following investigation. In order to sufficiently absorb the pressure fluctuation of the ink in the subtank, it is necessary that the areal size of the damper film should be increased. However, if a damper film having a large areal size is provided for the subtank, then the areal size of the gas-permeating film is decreased to an extent corresponding thereto, and it is feared that the gas contained in the subtank cannot be discharged sufficiently. As a result, the gas flows into the ink-jet head together with the ink. It is feared that the discharge characteristic of the ink may be fluctuated in the ink-jet head. On the other hand, if it is intended to increase both of the areal sizes of the damper film and the gas-permeating film, the subtank consequently has a large size.